Early Validation of Gomos Limb Products Altitude Registrationby Backscatter Lidar using Temperature and Density Prou0002les

摘要

One basic need for all limb data products is the correct registration of the altitude for each measurement level. The validationrnof profile products has to comprise beyond the comparison of absolute values also an inspection of the altitudernregistration assigned to the measurement values. Lidar instruments are particularly suitable to perform this kind of validationrndue to a very precise determination of altitude as well as an high altitude resolution. Several lidar instruments arernincluded in the validation activities, however, at this early validation stage there are only two contributions to the validationrnof limb products altitude registration. One contribution is by the University of Bonn Lidar at the Esrange (Sweden)rnand the other by the York University Lidar at Toronto (Canada) presently run by the Meteorological Service of Canadarn(MSC). In a campaign lasting from mid July to the end of August validation measurements for Envisat atmospheric productsrnwere carried out with the University of Bonn backscatter lidar at the Esrange (68N, 21E) near Kiruna in northernrnSweden. Temperature and density profiles of Gomos level 2 products processed with software version GOPRrnLV2 5.3rnwere used for comparison with lidar relative density and absolute temperature profiles to obtain information on the altitudernregistration of Gomos data products. Calculating the cross correlation function of corresponding Gomos and lidar profilesrnyields altitude-shifts for the maximum cross correlation coeffiient. This altitude-shift reveals information on the Gomosrnaltitude-registration. Using the density data for comparison shows a perfect agreement in altitude-registration betweenrnGomos and lidar whereas the comparison using temperature data results in slight altitude-shifts with a median value ofrn-300 m. Larger altitude-shifts up to 1.7 km were observed in some individual cases. These altitude-shifts are not causedrnby an error in the Gomos altitude registration, but by different profile-shapes for the lidar and Gomos data; lidar datarnfrequently show wave patterns, whereas Gomos data are rather smooth and do not show such patterns.rnComparison with the temperature data of the Toronto (44N, 80W) lidar are available for three Gomos occultations, two inrnJuly, one in October, processed also with software version GOPRrnLV2 5.3. Although the Gomos data are very noisy therncalculation of the cross correlation function was carried out. All comparisons show an altitude-shift of +3 km and evenrnmore between lidar and Gomos altitude registration.